Pentax PF-85 EDa review (2 Viewers)

[Jesus2024]

Hello everyone

First of all I want to apologize if any sentence of my review is not well understood,I speak little English so I am helping myself with the translator. This is the first time I write in the forum but I have been reading the contributions for more than 2 years and thanks to all the forum members who wrote their messages I bought the small Pentax PF-65 eda II,a purchase that has given me many moments of joy. 3 months ago I bought online the new Pentax PF-85 and I wanted to contribute to the forum my experience of using it during this time. I am not a professional nor do I understand much about technical parameters like other forum members,neither have I done any star tests for fear of being wrong,so I will just talk about the basics. The first thing I wanted to say is that the reason I bought the PF-85 even though I was very happy with the PF-65 is because here in Spain,and especially where I live,a spotting scope can only be used well 1 hour after sunrise and 1 hour before sunset,the rest of the day the refraction due to the heat is a problem. Can you use it?, of course, but the experience is not the same. As I said before I am very happy with my PF-65,and there is not a single species that I have not been able to identify with it,but during those hours at dawn and dusk those extra 20mm of the PF-85 make the difference between “enjoy” and “identify”,with the PF-85 and the XW-14 eyepiece I can see at a considerable distance,for example,the color of the legs or the color of the beak of the birds,something that with the PF-65 is almost impossible,being able only to identify the species. As for the general view with the PF-85 I must say that in combination with the Pentax XW-14 eyepiece (36x) that I use it is very sharp and bright, being at the same level of telescopes of much more expensive brands. In my case this is my third telescope but it is the first one I have with central wheel focus and the truth is that I was a little reluctant before buying it in case I didn't like this system, but the truth is that it works very well and after a few days of use I was already used to it. As for the chromatic aberrations, they are present in the PF-85 in the same way as in the PF-65, in this parameter there is no improvement in the PF-85 (at least in the unit I have) with respect to the old PF-65. In high contrast situations (for example a starling perched on a backlit roof) if you observe in the center of the field of view the chromatic aberrations are very well controlled,almost nonexistent,but if you move the telescope to one side or the other or up or down,when you get close to the edge you can observe some purple or green lines. But I repeat that this has only happened to me in high contrast situations. However I must say that this happens to me using the XW-14 eyepiece which has relatively low magnification (36x), I don't know if with a zoom eyepiece or another eyepiece of higher magnification the chromatic aberrations will be more noticeable. Now I want to talk about 2 things about the PF-85 that I didn't like. The first one is the carrying and tripod use case included in the price and that is very similar to the one that comes with the PF-65 but there is in my opinion an important difference, the PF-65 has a focus knob and being on the top of the telescope the folds of the case do not bother when you are focusing so it can be used on the tripod, however in the case of the PF-85 having a central focus wheel the folds of the case do not allow to focus easily, it can be done, but in my opinion it is not comfortable to do it. I think Pentax could have taken more care in this aspect and made a more open holster in the style of the Zeiss Gavia or the Swarovski ATS. The other thing I don't like is that the PF-85 unlike the PF-65 doesn't have a highlight/guide on the lens hood to help you locate distant birds. It seems silly but it is something that has helped me a lot in some occasions, the truth is that when I bought the telescope I didn't pay attention to this detail when I looked at the photos, I just assumed that as the PF-65 had it in the PF-85 it would also be like that. And now I am going to expose my final conclusions. Is it worth buying the PF-85 if you already have the PF-65?, well in my opinion, absolutely YES. As I explained above there are situations where that extra 20mm of aperture makes the difference between “enjoying” the birds or just “identifying” the birds. I believe that neither of the 2 telescopes can replace the other but that both complement each other perfectly, now I use the PF-85 for birding on short trips where I can get there by vehicle, and I have left the PF-65 for long trips on foot or trips where weight and volume are determinant, knowing that this “little guy” will be up to the task of identifying birds in any situation. Is it worth buying the PF-85 if you already have the old PF-80?, because in this case I have my doubts. I have not had the opportunity to look at the PF-80 but many forum users agree that it is a very good telescope, so the reasons to buy the new PF-85 would then be a smaller volume and less weight, because optically I do not think there is much difference, so then the decision would be already very personal. Finally I bought the PF-85 without eyepiece for 1400 euros,because I am not a big fan of zooms and I wanted to take advantage of one of the two eyepieces I already used with the PF-65,in this case I am using the XW-14 on the PF-85 and I have left the XF-12 to use it with the PF-65. Anyway,thank you very much to all of you for reading my review and within my limitations I hope to have helped some forum member in his decision to buy or not this telescope as 2 years ago the messages of others helped me. A big hug from Spain to all of us who share this wonderful hobby.

Jesús.

 

[Tringa45]

Thanks for the report. It sounds as if you have found a good compromise for your viewing conditions.
More magnification would not only magnify the mirage problems but would result in a loss of brightness in twilight due to the reduced exit pupil.
I find it strange that "seeing" is often a topic with amateur astronomers but seldom with birders, and recall one situation on a sunny late summer afternoon, when my 30x scope was showing no more detail than my 10x binocular!
The chromatic aberration you notice is lateral CA and is caused by the eyepiece. It is present to a greater or lesser degree in all eyepieces and cannot be fully corrected.
Lastly, I wonder if it would be better to use the XW-14 for your outings with the PF-65. A magnification of 28x is still very useful and you would not only have a slightly larger 2,3 mm exit pupil, but also increased apparent and true field of view.

John

 

[DRodrigues]

...
The chromatic aberration you notice is lateral CA and is caused by the eyepiece. It is present to a greater or lesser degree in all eyepieces and cannot be fully corrected.
...

The XWs eps aren't known by having CA. I never looked through a XW14 but have the XW20 and the XW5, that don't show CA. The CA seen should be from the scopes...

 

[DRodrigues]

... I don't know if with a zoom eyepiece or another eyepiece of higher magnification the chromatic aberrations will be more noticeable.
...

Yes, higher magnifications show more CA.
Since you see it with the XW, you might try other brand eps to see if helps - for instance my on my Optolyth 100 the XW5 work great and show less CA than with Optolyth eps...
An good alternative to the XWs, with larger AFOV (76º), lower cost (and are on sale), but not waterproof are the Baader Morpheus.
Regarding the zooms, it would be interesting to know if the Baader Hyperion zoom or the SVbony wide-field zoom would reach focus - the APM Superzoom shouldn't...

 

[Tringa45]

The XWs eps aren't known by having CA. I never looked through a XW14 but have the XW20 and the XW5, that don't show CA. The CA seen should be from the scopes...

David,
Longitudinal CA (centre field) is caused by the objective lens. Lateral CA (field edge) is caused by the eyepiece and will be present in all eyepieces.
However it may be masked by astigmatism and the XWs show this to a greater or lesser extent. Henry Link posted some graphs for the XWs some years ago. They all differed but on all of them the tangential and sagittal field curvature diverged towards the field edge.

John

 

[Jesus2024]

The chromatic aberration you notice is lateral CA and is caused by the eyepiece. It is present to a greater or lesser degree in all eyepieces and cannot be fully corrected.


John

Hi John.
Thank you very much for the information. I was unaware of this concept of lateral chromatic aberration and also that it is present in all eyepieces. I have also been able to verify it in another telescope.
This weekend I was bird watching in a lake near my house, and I met a bird watcher that I had never seen before and who had a Zeiss Harpia 85. After talking to him for a while, I asked him if I could look through his telescope, and I immediately looked for lateral aberrations and sure enough they were there. I couldn't see what magnification the eyepiece was at, but I don't think it was more than 40 or 45x.
I couldn't really observe for more than one or two minutes, but I thought I noticed that in the Harpia the percentage of the central field free of aberrations was lower than in my PF-85, and that as you get closer to the edge they were noticeable earlier than in my PF-85.
I was only carrying binoculars and I couldn't verify if this was really the case or just my perception. So I would like to ask you something that I am not clear about in case you or another forum member can help me.
The eyepiece of the Harpia is a zoom eyepiece, and in my PF-85 I use the fixed 36x XW-14.
Could it be that in a zoom eyepiece the percentage of the center of the field free of lateral aberrations is less than in a fixed eyepiece?
I ask this because although I am not a big fan of zooms, maybe in the future I will change my mind and buy one and I would not like that after spending the money the lateral aberrations are more noticeable than in my fixed eyepiece.
I repeat that maybe it was just my perception, but I was really surprised by the aberrations in an alpha telescope that costs 2000 euros more than my PF-85.
Greetings to you and to the other members of the forum.
Jesus.

 

[Tringa45]

Hi Jesus,

The Zeiss Harpia 85 you looked through is a rather strange animal.
It has a 7,5 mm wide angle eyepiece and a zooming objective lens with a focal length of 162-486 mm.
This enables it to have a constant apparent field of view of ca. 69° across the whole range of magnification. On conventional scopes with zoom eyepieces the AFoV is usually lower at lower magnifications.
The disadvantage is that at 22x magnification the exit pupil is only 2,5 mm, whereas with a conventional 85 mm scope you would expect nearly 4 mm.
This will be a handicap under poor lighting conditions.
I haven't seen any star tests or resolution tests of the Harpia scopes but it would surprise me if they matched the qualities of Swarovski and top Kowa models.
With scope objectives the off-axis rays are usually <1,5° so there would be little difference between on-axis and off-axis CA but on some eyepieces the off-axis rays are sometimes >30°, so it is almost impossible to eliminate lateral dispersion.
I have a 30xW eyepiece on my Swarovski ATM65 HD. It has 20 mm eye relief, a 65° AFoV, a flat field with no noticeable rectilinear distortion or astigmatism, but I still see some lateral CA.
However, I don't think zoom eyepieces have an inherent disadvantage with regard to lateral CA. The 25-60x eyepiece on my Kowa 883 is almost as well corrected as that 30xW with just a very small amount of astigmatism, and the AFoV at 25x is still an acceptable 57°.
Zoom eyepieces IMO make most sense on the larger scopes, where one has large exit pupils at the useful lower magnifications (>20x) in low light, and the ability to use higher magnifications if required under strong lighting conditions.
I know that some will disagree but think that there is not much to be gained terrestrially when exit pupils drop much below 1,5 mm due to a loss of brightness and the acuity of the observing eye.

Regards,
John

 

[Jesus2024]

I don't think zoom eyepieces have an inherent disadvantage with regard to lateral CA.

Hi John.
Thank you very much for your explanations, it is a pleasure to talk to people who know so much about the subject, I will keep them in mind if I ever buy a zoom eyepiece.
If it is not too much trouble I would like to ask you something else.
Do you think that the concept of sample variation can be applied to eyepieces (only the eyepiece, without the telescope body)? Do you think that "individually" there are "lemons or cherries" between eyepieces of the same model and brand?
I am very happy with my 2 Pentax eyepieces (XW-14 and XF-12), and also economically I cannot afford to buy another one right now, but I am still wondering if, for example, the lateral aberrations that we have discussed would be more (or less) noticeable in another XW-14 unit different from the one I have.
Thank you very much again.
Jesus.

 

[Tringa45]

Jesus,

Sample variation in scope objectives I think plays a much greater role in loss of image quality than in eyepieces.
Central image sharpness in some cheap eyepieces might be just as good as in more expensive and complex constructions, and amateur astronomers sometimes favour 3 or 4 element designs for certain applications because they expect better transmission and higher contrast.
The disadvantages are of couse a limited AFoV of 45-50° and short eye relief for the shorter focal lengths.
Using adapters I have tried various 1,25" astronomical eyepieces on my birding scopes but have not found any to match the edge correction of the dedicated eyepieces from the scope manufacturers. It's otherwise just very unlikely that the field curvatures of objective and eyepiece will be a perfect match.

John

 

[Jesus2024]

Jesus,

Sample variation in scope objectives I think plays a much greater role in loss of image quality than in eyepieces.
Central image sharpness in some cheap eyepieces might be just as good as in more expensive and complex constructions, and amateur astronomers sometimes favour 3 or 4 element designs for certain applications because they expect better transmission and higher contrast.
The disadvantages are of couse a limited AFoV of 45-50° and short eye relief for the shorter focal lengths.
Using adapters I have tried various 1,25" astronomical eyepieces on my birding scopes but have not found any to match the edge correction of the dedicated eyepieces from the scope manufacturers. It's otherwise just very unlikely that the field curvatures of objective and eyepiece will be a perfect match.

John

Hi John.
Once again a great technical explanation about eyepieces.
Thank you very much.
Best regards.
Jesus.

 

[wllmspd]

Using adapters I have tried various 1,25" astronomical eyepieces on my birding scopes but have not found any to match the edge correction of the dedicated eyepieces from the scope manufacturers. It's otherwise just very unlikely that the field curvatures of objective and eyepiece will be a perfect match.

John

Interesting that all non-OEM eyepiece will necessarily not be ideally corrected for spotting scopes of other manufacturers. How bad are the views round the edges likely to be, as the wider fields available can “add context” and make the view feel more immersive. Which scope/ep combinations do the best job?

So for a wide, fully corrected view the 57-70 degree and OEM magnifier from the OEM to get higher powersare likely to give the best views?


Peter

 

[Tringa45]

The major concern of using astronomical eyepieces on birding scopes is being able to focus to infinity. The Kowa 883 for example is not very tolerant of astro eyepieces and cannot achieve infinity focus with some. The adapters will sometimes restrict the available in-focus by another 5 mm.
Most astro eyepieces show pincussion distortion, some of them to quite an extreme extent. It is even desirable on the night sky but can be disturbing terrestrially.
After some quick tests my impression is that the field curvature of the scope's objective affects the edge sharpness less with shorter focal length (higher magnification) eyepieces.

John

 

[K-day]

Jesus, I recommend moving on from the Pentax eyepieces.

For terrestrial use what I found is most important to me is sharpness. After comparing many fixed length eyepieces, including Pentax WX & XFs, the sharpest was and is the Noblex/Docter UWA 12.5mm. An eyepiece that is almost as sharp is the Sky Rover HFW 12.5mm. I haven't used APM's version the Hi-FW, but it is made by the same manufacturer KUO, so I would assume it would perform the same.

The Baader Morpheus 12.5mm wouldn't fit my eyepiece holder so I can't comment on it, but many praise it for both terrestrial and astronomical use.

 

[Tringa45]

For terrestrial use what I found is most important to me is sharpness. After comparing many fixed length eyepieces, including Pentax WX & XFs, the sharpest was and is the Noblex/Docter UWA 12.5mm. An eyepiece that is almost as sharp is the Sky Rover HFW 12.5mm. I haven't used APM's version the Hi-FW, but it is made by the same manufacturer KUO, so I would assume it would perform the same.

Have you actually compared these on the scope in question?
In the Binomania test it was also stated that the objective lens has the overriding effect on sharpness (resolution).
Different eyepieces of the same focal length on the same scope may show differences in AFoV, edge correction and eye relief, but it is a wild exaggeration to state that there would be a visible difference in central sharpness at a mere 38x magnification.

 

[K-day]

Have you actually compared these on the scope in question?...

No.

I compared eyepieces using a Sky Rover 70 APO BINO, 400mm focal length, 70mm aperture, SD objective lens. For the primary evaluation the control eyepiece was the Sky Rover HFW 12.5mm @ 32X in one side, and the variable eyepiece in the other. Most of the eyepieces were also put in cross comparisons to each other. Fixed daytime distances of 15m, 300m, and 340m. Nikon SW and Baader Morpheus eyepieces would not insert past the compression ring, btw.
Magnifications:
22X Sky Rover UF 18mm
32X Noblex UWA 12.5mm, Sky Rover HFW 12.5mm
33X Pentax XF 12mm
36X TeleVue DeLite 11mm
40X Sky Rover UF 10mm
47X Pentax XF 8.5 mm
50X TeleVue Ethos 8mm
57X TeleVue DeLite 7mm, Pentax SMC XW 7mm
67X TeleVue Ethos 6mm, Siebert Optics Custom SS4 6mm

 

[Jesus2024]

Jesus, I recommend moving on from the Pentax eyepieces.

Hello.
Thank you very much for the information and the links.
I cannot afford to buy another eyepiece now,
I didn't know about those brands either, but if I ever decide to change my eyepiece I will keep them in mind.
Regards.
Jesus.

 

[Tringa45]

No.

I compared eyepieces using a Sky Rover 70 APO BINO, 400mm focal length, 70mm aperture, SD objective lens. For the primary evaluation the control eyepiece was the Sky Rover HFW 12.5mm @ 32X in one side, and the variable eyepiece in the other. Most of the eyepieces were also put in cross comparisons to each other. Fixed daytime distances of 15m, 300m, and 340m. Nikon SW and Baader Morpheus eyepieces would not insert past the compression ring, btw.
Magnifications:
22X Sky Rover UF 18mm
32X Noblex UWA 12.5mm, Sky Rover HFW 12.5mm
33X Pentax XF 12mm
36X TeleVue DeLite 11mm
40X Sky Rover UF 10mm
47X Pentax XF 8.5 mm
50X TeleVue Ethos 8mm
57X TeleVue DeLite 7mm, Pentax SMC XW 7mm
67X TeleVue Ethos 6mm, Siebert Optics Custom SS4 6mm

That's an impressive array of eyepieces. However, I'm not sure that left/right comparisons, particularly at high magnifications, would be entirely fair.
AFAIK some binoscopes adjust collimation by the eccentric rotation of one objrctive, so the ultimate resolution of left and right barrels might differ.

There will not be much difference over various testing distances. I think someone suggested 50 focal lengths (in your case 20 m), or was it 100?
In any event, I tested the resolution of my two birding scopes at an arbitrary distance of 23 m and one was diffraction limited and the other close.

Ther will be insignificant differences in central sharpness between eyepieces. If you think you saw a difference, then I suggest you set up a well-illuminated and high contast target such as a 1951 USAF chart at >20 m. You will then be able to quantify the amount of detail yo can see. If you then placed a low magnification monocular (2-4x) behind the eyepiece(s), you would see more detail indicating that the limitations were your own eyesight and not the eyepieces.

John

 

[K-day]

For whatever its worth, Harry Siebert aligned and collimated my BT, plus adjusted the focal point for my primary bird watching distances. I couldn't do anything about aberrant concentricity within an eyepiece other than clock the eyepiece to test and partially correct for it if detected. Differences between tubes were accounted for by simply swapping sides. Chart testing was impractical given where the birds perch. I used embossed/as-cast letters & numbers on power tower steel beams & strain links, fastener threading, fastener head marks, and cable strand separation for objective comparisons in leu of a chart. There is also lettering on cast hardware on the wood utility poles. Starlings are subjects I often look at on the power towers and they're good for comparing things like color fringing, tone, and contrast. They also like to perch in the shade where some eyepieces didn't do well peering into.

I left out a TeleVue Delos 10mm in the comparison list. Here is an example of a an equal FL comparison in 10mm. That little Sky Rover was in my third place row of contenders btw, the Delos was not.

 

[DRodrigues]

Jesus, I recommend moving on from the Pentax eyepieces.

For terrestrial use what I found is most important to me is sharpness. After comparing many fixed length eyepieces, including Pentax WX & XFs, the sharpest was and is the Noblex/Docter UWA 12.5mm. An eyepiece that is almost as sharp is the Sky Rover HFW 12.5mm. I haven't used APM's version the Hi-FW, but it is made by the same manufacturer KUO, so I would assume it would perform the same.

...

Not the best advice...
Your bino telescope is much less corrected (it's a doublet, so with more curved field...), than the Pentax scope!
Also, XW and XF eps are very different.
Any comparison of eps must be done with this scope model and not with a different scope or telescope!
Noblex/Docter eps are some of the best ep ever made! It's nice to know the HFW is almost as good.
I have a Nikon HW 12.5, that is also one of the best ep, but isn't so useful for daylight and even doesn't work so well with my day-light astro-combo See HW 12.5 section since shows too much the field curvature of the astro combo, and the TMB92 is a triplet...
By the way, don't have a Noblex/Docter since have the Nikon HW and the ES92 12mm, that have wider AFOV/FOVs than the Noblex/Docter. If there was a Noblex/Docter 5mm, I probably would get one...

 

[K-day]

Jesus, I recommend moving on from the Pentax eyepieces...

Not the best advice...

...Since you see it with the XW, you might try other brand eps to see if helps...